The present invention relates to an infusion pressure monitoring system for a phacoemulsification or vitrectomy system.
A typical surgical instrument suitable for phacoemulsification procedures on cataractous lenses includes an ultrasonically driven phacoemulsification hand piece, an attached hollow cutting needle surrounded by an irrigating sleeve, and an electronic control console. The hand piece is attached to the control console by an electric cable and flexible tubing. Through the electric cable, the console varies the power level transmitted by the hand piece to the attached cutting needle. The flexible tubing supplies irrigation fluid to the surgical site and draws aspiration fluid from the eye through the hand piece.
During a phacoemulsification procedure, the tip of the cutting needle and the end of the irrigation sleeve are inserted into the anterior segment of the eye through a small incision in the eye's outer tissue. The surgeon brings the tip of the cutting needle into contact with the lens of the eye, so that the vibrating tip fragments the lens. The resulting fragments are aspirated out of the eye through the interior bore of the cutting needle, along with irrigation fluid provided to the eye during the procedure, and into a waste reservoir.
Throughout the procedure, irrigating fluid is infused into the eye, passing between the irrigation sleeve and the cutting needle and exiting into the eye at the tip of the irrigation sleeve and/or from one or more ports or openings formed into the irrigation sleeve near its end. This irrigating fluid is critical, as it prevents the collapse of the eye during the removal of the emulsified lens. The irrigating fluid also protects the eye tissues from the heat generated by the vibrating of the ultrasonic cutting needle. Furthermore, the irrigating fluid suspends the fragments of the emulsified lens for aspiration from the eye.
Conventional systems employ fluid-filled bottles or bags hung from an intravenous (IV) pole as an irrigation fluid source. Irrigation flow rates, and corresponding fluid pressure at the eye, are regulated by controlling the height of the IV pole above the surgical site. For example, raising the IV pole results in a corresponding increase in head pressure and thus increase in fluid pressure at the eye, resulting in a corresponding increase in irrigation flow rate. Likewise, lowering the IV pole results in a corresponding decrease in pressure at the eye and corresponding irrigation flow rate to the eye.
Aspiration flow rates of fluid from the eye are typically regulated by an aspiration pump. The pump action produces aspiration flow through the interior bore of the cutting needle. The aspiration flow results in the creation of vacuum at the aspiration line. The aspiration flow and/or vacuum are set to achieve the desired working effect for the lens removal. The IV pole height and infusion pump are regulated to achieve a proper intra-ocular chamber balance in an effort to maintain a relatively consistent fluid pressure at the surgical site within the eye.
While a consistent fluid pressure in the eye is desirable during the phacoemulsification procedure, common occurrences or complications create fluctuations or abrupt changes in fluid flow and pressure at the eye. These fluctuations or changes occur for a number of reasons. For example, depleting the fluid reservoir, inadvertently separating the irrigation line and hand piece, leaking fluid from the line or from a connector between lines, and kinking the irrigation line can all result in pressure fluctuations or abrupt pressure changes leading to surgical complications.
Some of today's systems are equipped with irrigation/infusion pressure sensors, which have the ability to monitor the infusion pressure and forewarn the user of pressure drops. These systems monitor relative to a fixed reference point. For example, the system may detect when the pressure falls below a set, single pressure value for all points during a surgical procedure. Since this set, single pressure value is of necessity somewhere below the lowest expected pressure for a surgical procedure, in some instances, a complication arising when the pressure is high may not be detected until after substantial drop in pressure, resulting in a relatively slow reaction time. A slow reaction time may result in, among other undesirable complications, shallowing or collapse of the anterior eye chamber and possible thermal event to the cornea (if ultrasound is in use) at the incision site due to the reduced or eliminated irrigation flow.
Therefore, there remains a need for an improved system response to unexpected pressure drops that can occur during a medical procedure. The present disclosure is directed to addressing one or more of the deficiencies in the prior art.